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The discussions showed a clear understanding of the need for the development of specific on-line sensors which could provide necessary real-time information on process variables. Some needs in the areas of modeling were identified; these were more general in nature. There was little expression of need for (or understanding of) intelligent control systems. The lack of comprehensive understanding of nearnet shape casting processes is clearly reflected in these latter areas.
Eight sensors were identified as critical to the successful development of a commercial strip casting process. It was recognized that each of these must be employed in a manner in which it could be actively used to control the outcome of the process, and not merely in a passive role to provide information. Attempts were made to determine the range and precision needed for each of the sensors. In many cases, the identified range was quite accurate, but the estimated precision reflected that required of the product; the sensor may require greater sensitivity. For example, if the thickness of a strip is required to be controlled to within 2 percent of its nominal thickness, the measuring sensor must be able to detect a variation of possibly one tenth of that amount in order to effect proper control. The sensor needs were prioritized as follows:
1. Rapid On-line Strip Thickness and Profile Sensing
Short time constant, 20X today's technology
3. Continuous Temperature Mapping of the Substrate Surface
- +/- 5 °C
4. On-line Hot Strip Inspection System
5. Liquid Metal Inclusion Sensor
6. Continuous Temperature Measurement of the Melt
- +/- 1 °C
It bears repeating that the specifications listed with each of these sensors reflects the limits of control that must be met to produce satisfactory strip. The participants agreed that additional investigation of each of these sensors is necessary to determine operational specifications required of each. The discussions were specifically steered away from including potential solutions to each of the needs; this was not the intent of the session.
In the area of mathematical modeling, it was agreed that most models are processspecific. Nonetheless, there exist many commercially available models of the two principal phenomena involved in near-net shape casting, heat transfer and fluid flow. It was determined after considerable discussion that the industry would benefit from a comprehensive review of such models currently available, along with their respective strengths and weaknesses, and a strategy for implementation of selected models. Such a review would assist research groups undertaking projects in this area.
INTELLIGENT PROCESS CONTROL
In the area of process control, it was recognized that the overall state of knowledge of near-net shape casting makes it difficult to design a comprehensive control system at this stage of development. It was determined that it would be meritorious to undertake an intelligent process simulation project to serve as a model for the metals industry. Such a project would introduce many of the features of intelligent processing to the primary metals industry, while simultaneously assist in defining the specifications required for specific sensors.
An extension of this project might involve commissioning the development of an expert system shell, specifically designed for strip casting. It was overwhelmingly agreed that it would not be desirable to attempt to modify an existing shell designed for another process.
The interactive discussions that accompanied the session led to the clear observation of the necessity for industry to take the lead role in defining the specifications required of each sensor, particularly in regard to the constraints imposed by the operating environment.
Shortly, after the close of the Workshop, correspondence was received from a participant from the copper industry (B. G. Lewis) expressing observations of similarities and differences between the perceived need of the copper and steel industries. These observations are summarized in table 1.
Prepared by: W. Eugene Eckhart, Jr.
TABLE 1. Copper-base Alloys: Near-Net Shape Casting
Melt level sensor.
20 Cast strip temperature.
3 3 3
The high thermal conductivity of copper